geology midterm2

geology midterm2 - Emsellem 1 Geology midterm#2 Chapters...

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Emsellem 1 Geology midterm #2 Chapters 6,7,9 Igneous Rocks Volcano = vent at which melt from inside the Earth spews onto the planet’s surface i.e. has a volcanic eruption Lava = melt from the volcanic eruption above earth’s surface o Rapid cooling o Fine grained o Extrusive o volcanic Magma = igneous rocks, melt that solidifies under the surface o Slow cooling o Coarse grained o Intrusive o Plutonic Aluminum, calcium, sodium, potassium, iron, and magnesium Wet magmas: up to 15% dissolved volatiles such as water, carbon dioxide, nitrogen, hydrogen, and suflur dioxide – come out of earth at volcanoes o Water constitutes 50% of gasses erupted o Carbon dioxide 20% Igneous rocks o All rocks that were formed by the solidification of molten rocks Source of material = melting of rocks in hot, deep crust and upper mantle Composition of a melt reflects the composition of the solid from which it was derived, all magmas form from different source rocks therefore have different compositions Rock-forming process: crystallization = solidification of magma Magma changes composition as it cools because of the formation and sinking of crystals preferentially remove certain atoms from the magma (fractional crystallization) o Freeze at high temperatures 650-1100 C Intrusive igneous rock = rock made by the freezing of magma underground that has pushed its way into preexisting rock of the crust Extrusive igneous rocks = rocks that form by freezing of lava above ground, extrudes onto the surface and comes in contact with atmosphere or ocean o Include both solid lava flows and deposits of pyroclastic debris Pyroclastic debris: o Form when clots of lava fly into the air and then freeze to form solid chunks before hitting the ground o Form when the explosion shatters preexisting rock and ejects fragments onto the countryside o Form when an explosion blasts a fine spray of lava into the hair and it instantly freezes to form fine particles of glass i.e. ash
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Emsellem 2 Earth’s heat Comes from: o 1. nebula theory: collision of plants i.e. kinetic energy of colliding plantesimals transformed into heat energy o 2. collisions – mars-sized object collided with formed earth o 3. radioactivity: decay of radioactive atoms Atoms of radioactive elements spontaneously disintegrate by emitting subatomic particles. As these particles are absorbed by the surrounding rocks their energy of motion (kinetic) is transformed into heat (thermal) Changes in pressure, volatile content, and temperature trigger melting in the upper mantle and lower crust Silicates Magmas contain silicon and oxygen i.e. silicates! Many silicate minerals melt at the temperatures and pressures reached in lower parts of the curst and the mantle o Quartz o Feldspar: K-feldspar and plagioclase feldspar o Mica o Pyroxene o Amphibole o Olivine How igneous rocks differ from one another Texture: depends on cooling rate o Extrusive (volcanic) are rapid cooling: know this because of the fine-grained and
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geology midterm2 - Emsellem 1 Geology midterm#2 Chapters...

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